At the present time, many power supplies are designed to operate on both 110 volt and 200 volt power supplies as their input. However, to so operate, the power supply is provided at its input with a removable strap which is switched into operation for one supply and is removed for the other supply. This is an undesirably expensive and awkward arrangement to manipulate.
The present invention provides a simple and inexpensive circuit arrangement for permitting a power supply to operate properly and automatically whether the input supply voltage is 110 volts or 220 volts. The circuit arrangement includes a voltage-controlled current generator which acts like a variable negative resistor coupled to a diac and triac.